Two speed transmission with brake

ABSTRACT

The invention is a two speed transmission including first and second shafts independently rotatably journaled in a housing and coupled together with an epicyclic gear assembly. The epicyclic gear assembly includes a ring gear and a sun gear one of which is coupled to a predetermined one of the first and second shafts and at least one pinion gear coupled to the other of the shafts for rotation therewith. Brake means are coupled to the other of the ring and sun gears for selectively locking and unlocking same against rotation, and self-actuating clutch means are provided for coupling the aforementioned other gear to the pinion gear. The clutch means includes spring means for forcibly engaging the clutch when the aforementioned other gear is unlocked and a helical spline means for forcibly frictionally disengaging the clutch means in response to locking the aforementioned other gear.

[ Oct. 9, 1973 United States Patent 1191 Crooks TWO SPEED TRANSMISSIONWITH BRAKE ABSTRACT [76] Inventor: James W. Crooks, 4973 N. Larkin' StWhitef sh Bay, Wis. 53217 Oct. 14, 1971 [22] Filed:

Appl. No.: 189,380

pled to a predetermined one of the first and second shafts and at leastone pinion gear coupled to the other of the shafts for rotationtherewith. Brake means ,74/751 192/7028, 188/712 Int. [58] Field of [52]US. 192/4 A F16| 57/10 are coupled to the other of the ring and sungears for 192/4 A 4 R selectively locking and unlocking same againstrotation, and self-actuating clutch means are provided for Ru Ci dcoupling the aforementioned other gear to the pinion UNITED STATESPATENTS gear. The clutch means includes spring means for forciblyengaging the clutch when the aforementioned 192/4 A 11/1943 192/4 R gearlocked and a helm splme means forcibly frictionally disengaging theclutch means in Primary Examiner Benjamin w wyche response to lockingthe aforementioned other gear. AttorneyI-Iarold B. Hood et al. 25 Claims3 Drawing Figures III III!

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1 vi twI/I/ 5 13b II! III In PATENTED BET 9l973 3,763,978

BY MM,

ATTORNEYS TWO SPEED TRANSMISSION WITH BRAKE BACKGROUND OF THEINVENTION 1. Field of the Invention The invention relates to a gearedtransmission utilizing an epicyclic gear assembly and in particular, isa two speed transmission having a mechanical clutch and incorporatingcompression springs and helical splines to effect engagement anddisengagement thereof.

2. Description of the Prior Art Multiple ratio geared transmissionsutilizing epicyclic or planetary gear assemblies are well known.Typically, such transmissions utilize a brake mechanism and a clutchmechanism coupled to and between a predeterminedones of the gears of theepicyclic gear assembly, respectively, the brake and clutch mechanismsbeing alternately engaged and disengaged by means of hydraulic ormechanical devices to change the drive ratio of the transmission.

In one such prior art transmission, the epicyclic gear assemblyincorporates helical gears and the axial thrust on the gears is utilizedto engage or disengage the clutch mechanism. Correspondingly, a separatemechanism is required to operate the clutch into its opposite mode, thislatter mechanism typically including a hydraulic device, one way clutch,or an independent mechanical linkage.

SUMMARY OF THE INVENTION The present invention is a two speed, gearedcoupling or transmission operable between a first condition in which itprovides a differential gear ratio between first and second shafts,thesenormally being the input and output shafts, and a second condition inwhich it provides a unity ratio therebetween. The coupling is providedwith a first and second shaft independently rotatably journaled in ahousing and coupled together with an epicyclic gear assembly whichincludes a ring rear, a sun gear, and at least one pinion or planetarygear. One of the ring and sun gears is fixedly secured to the firstshaft and the pinion gear is coupled to the other shaft. Coupled to theother of the ring and sun gears is a brake means for selectively lockingand unlocking same from rotation. Coupled between the last men tionedgear and anotherof the gears of the epicyclic gear assembly is a clutchmeans for selectively locking the aforementioned other gear to thepinion gear when the brake means is in an unlocked condition. The clutchmeans is self-actuating and includes a helical spline means responsiveto locking the brake means, and spring means responsive to unlocking thebrake means for forcibly disengaging and engaging the clutch means,respectively.

It is therefore an object of the invention to provide an improved twospeed transmission which provides a differential and a unity ratiocoupling;

It is another object of the invention to provide such a transmissionhaving a manually operable brake and a clutch whereby only the brakemeans must be actuated to selectively operate the transmission betweendifferential and unity ratios;

It is yet another object of the invention to provide such a transmissionin which a helical spline is utilized to deactuate the clutch means;

It is still another object of the invention to provide such atransmission in which the torque transmitting capability of the clutchmeans in the braking mode of transmission operation increases inproportion to the braking load on the transmission;

It is still another object of the invention to provide such atransmission in which the clutch is entirely mechanically actuated;

It is another object of the invention to provide a transmission thatprovides a positive coupling between the input and outputshaft for bothpositive and negative loads therebetween.

BRIEF DESCRIPTION OF THE DRAWINGS The above-mentioned and other featuresand objects of this invention and the manner of obtaining them willbecome more apparent and the invention itself will be best understood byreference to the following description of an embodiment of the inventiontaken in conjunction with the accompanying drawings, wherein:

, FIG. 1 is an axial-sectional view of a two speed transmission inaccordance with the invention.

FIG. 2 is a fragmentary partial cut away view showing details of thespline means.

FIG. 3 is'a fragmentary partial cut away view. showing details of amodification of the invention.

DESCRIPTION OF A SPECIFIC EMBODIMENT Referring now to the drawings thereis illustrated a two speed geared transmission or coupling 10 comprisinga housing 12 having front and :rear sections 14 and 16, respectively,which are secured together with a plurality of threaded fasteners as at18. A first shaft 20 is rotatably carried in housing 12 and includes amajor portion 24 and a reduced diameter pilot portion 26. A second shaft30 is also rotatably journaled in housing 12 by means of a sealed ballbearing assembly 32 and is provided with a cylindrical bore 34 whichreceives first shaft pilot portion 26 and is rotatably supported thereonwith a plurality of needle bearings as at 36. Axial thrust between firstshaft 20 and second shaft 30 is counteracted by a thrust bearing 38therebetween. An internal ring gear 40 having spur teeth 42 is drivinglycoupled to first shaft 20 by welding as at 44.

A hollow cylindrical brake shaft 46 has a stepped diameter bore 48 andis rotatably carried on first shaft 20 by means of a plurality of needlebearings 50. First shaft 20 and brake shaft 46 are further rotatablycarried in housing 12 by means of a second sealed ball bearing assembly52 and axial thrust on the brake shaft 46 is carried by sealed ballbearing 52 and a needle thrust bearing assembly 54, the latter beingdisposed between end 56 of brake shaft 46 and annular flange 58 of ringgear 40.

Brake shaft 46 has an end 60 distal to end 56 which extends outwardly ofhousing 12. A dish shaped brake disk 62 is provided with an annular,splined hub 64 whereby it is drivingly secured to end 60 of brake shaft46 by means of complementary splines 66 thereon.

Fixedly secured to housing 12 by means of a bracket 70 and threadedfastener 72 is a conventional caliper brake assembly 74, caliper brakeassembly 74 being of the type which is selectively manually operablebetween a first position in which it: is disengaged from brake disk 62and a second position in which it clampingly engages brake disk 62. Itcan now be observed that when brake caliper 74 is disengaged from brakedisk 62, the latter is freely rotatable within housing 12 and,conversely, when caliper brake 74 is engaged with brake disk 62, brakeshaft 46 is locked against rotation.

Fixedly secured to inner end 80 of second shaft 30 is a pinion gearcarrier 82 which comprises a drum member 84 fixedly secured to end 80 ofoutput shaft 30 as by welding, an annular pinion gear mounting flange 86and a clutch member mounting hub 88. The drum 84, pinion flange 86, andclutch hub 88 are fixedly secured together with annular gaskets 90 and92 therebetween by means of suitable threaded fasteners 94. Fasteners 94have enlarged heads 96 and distally disposed, threaded portions 98 whichextend outwardly from clutch hub 88 in a direction parallel to the axisof brake shaft 46 for a reason to be explained below.

A plurality of pinion gear shafts 100 are mounted on pinion flange 86 inan annular array and fixedly secured thereto by means ofa suitablekeeper 102 and snap ring 103. Rotatably carried on each pinion gearshaft 100 is a pinion or planet gear 104 having spur gear teeth 106which are operatively meshed with the teeth 42 of ring gear 40 inconventional manner, pinion gears 100 being held against axial movementby the enlarged heads 108 of pinion shafts 100.

Coaxially received on brake shaft 46 is a sun gear 110 which is securedthereto for rotation therewith by means of an internal male spline 112on sun gear 110 and a complementary, external female spline 114 on brakeshaft 46. As best seen in FIG. 2, splines 112, 114 are formed in aleft-handed helix, that is in a direction of a left-handed screw thread,and female spline 114 on brake shaft 46 is longer than male spline 112on sun gear 110 whereby sun gear 110 is able to move axially withrespect to brake shaft 46 to a limited extent.

A clutch assembly 120 includes a pressure member 122, a backup member124, and a driven member 126. Pressure member 122 and backup member 124are provided with concentric, frusto-conical friction surfaces 128, 130,respectively, and clutch driven member 126 includes s a frusto-conicalportion 134 disposed coaxially therebetween. Secured to frutso-conicalportion 134 are aplurality of friction-increasing linings 136, 138.Driven member 126 further includes an annular flange portion 140 whichhas therethrough a plurality of holes 142 in an annular array which areslidably received on ends 98 of threaded fasteners 94 whereby clutchdriven member 126 is drivingly coupled to pinion carrier 88 for rotationtherewith and is axially movable with respect thereto.

Clutch backup member 124 is received on and keyed to brake shaft 46 witha suitable key element 49 and secured against axial movement thereon byshoulder 148 of brake shaft 46 and a suitable snap ring 150 which isresiliently engaged within an annular groove 152 in brake shaft 46.

A plurality of mounting pins 156 having enlarged heads 158 are fixedlysecured to clutch backup member 124 in an annular array by means ofsuitable retaining clips 160. Pins 156 extend through suitable holes 162which are provided in clutch pressure member 122 in registry with pins156. Holes 162 are of larger diameter than pins 156 to allow forlimited, rotational movement between clutch pressure member 122 andclutch backup member 126 for a reason to be explained below. Received onpins 156 are flat washers 164 and a helical compression spring 166 iscompressibly fitted between enlarged heads 158 of pins 156 and washers164. It will now be apparent that springs 166 will resiliently urgeclutch pressure member 122 to the left as viewed in FIG. 1.Correspondingly, because clutch driven member 126 is axially movable byreason of its sliding fit on ends 98 of threaded fasteners 94, springs166 will urge clutch members 122, 126, and 124 into frictionalengagement with each other.

A suitable snap ring 170 is secured within an annular groove 172 inclutch mounting hub 88 and an annular wave spring 174 is compressiblyreceived between snap ring 170 and mounting hub 88. It will now beapparent that when clutch pressure member 122 is forcibly moved to theright (as viewed in FIG. 1), wave spring 174 will forcibly move clutchdriven member 126 to the right (as viewed in FIG. 1) and out offrictional engagement with clutch backup member 124. Wave spring 174 isselected such that it exerts a disengaging force less than the engagingforce exerted by springs 166 and such that it will move clutch drivenmember 126 in an amount just sufficient to prevent frictional contactbetween friction lining 136 affixed thereto and clutch backup member124.

Clutch pressure member 122 and clutch backup member 124 are providedwith concentrically disposed hub portions 176, 178, respectively, whichare drivingly coupled together by means of mating splines 180, 182. Asbest seen in FIG. 2, splines 180, 182 are again formed in a helix.However, splines 180, 181 are righthanded, i.e., in the direction of aright-handedscrew thread, and extend at a helix angle which ispreferably less than the helix angle of the splines 112, 114. It shouldbe noted that spline 180, which is on hub portion 178, is axially longerthan the spline 182 and sufficient clearances are provided between therespective hub portions 176, 178 whereby clutch pressure member 122 canmove axially with respect to backup member 124.

The sun gear is a part separate from hub portion 176, and is providedwith an internal bore 111 which receives coaxially a helical compressionspring 113. This spring 113 yieldably urges the sun gear 110 leftward onshaft 46 by bearing against a snap ring on shaft 46 and shoulder 117 inthe bottom of bore 111.

A resilient seal 184 is frictionally secured within a suitable bore 186in clutch mounting hub 88 and slidably engages the outside periphery ofclutch pressure member 122. Similar seals 188, 190 form fluid tight,sliding seals between clutch pressure member 122 and brake shaft 46, andbetween brake shaft 46 and first shaft 20, respectively. It can now beseen that brake shaft 46, second shaft 30, pinion carrier members 84,86, and 88, and clutch pressure member 122 define a fluid tight chamber192 which encloses ring gear 40, pinion gears 104, sun gear 110, andneedle bearings 36, and 50. This chamber is partially filled with asuitable liquid lubricant to lubricate the aforementioned gears andbearings, and, because chamber 192 is sealed, lubricant is preventedfrom passing therefrom to contaminate clutch friction linings 136, 138.

A sheave 194 is fitted to first shaft 20 and a toothed drive element 196is secured to second shaft 30 for rotation therewith, respectively,drive element 196 being partially enclosed within a suitable protectivecover 198.

Generally, during operation of the coupling 10 in direct drive, clutchis positively engaged thereby locking sun gear 110 against rotationrelative to the pinion gears 104 via clutch mounting hub 88 and pinionflange 86. With sun gear 110 locked to pinion gears 104, sun gear 110and pinion gears 104 are restrained from relative rotation and,correspondingly, pinion gears 104 are restrained from rotation withrespect to ring gear 40 thereby effecting a direct coupling therebetweento second shaft 30.

Upon application of caliper brake 74, sun gear 110 is restrained fromrotating, and, as will be explained in detail below, clutch 120automatically disengages. In this mode, pinion gears 104 will rotatebetween ring gear 40 and sun gear 110 thereby coupling first shaft tosecond shaft through a reduced ratio gear coupling.

In explaining the operation of the coupling, it is assumed that thefirst shaft 20 is being driven in a clockwise direction as viewed fromthe left of the transmission (as viewed in FIG. 1) and that there is aload on the second shaft 30 which resists rotation thereof.

To operate the coupling in direct drive, i.e., unity gear ratio betweenthe first and second shafts, 20, 24, respectively, caliper brake 74 isreleased thereby permitting brake disk 62 and brake shaft 46 to rotatefreely within housing 12. Because ring gear 40 is fixedly secured tofirst shaft 20 it also rotates in a clockwise direction. Assuming thatthere is a load on the second shaft 30, a torque is applied to thepinion carrier 82 thereby tending to restrain it from rotation. Consequently, the clockwise rotation of ring gear 40 applies a torque topinion gears 106 tending to make them rotate about pinion shafts 100.This in turn causes a counter clockwise torque to be applied to sun gear110. Under these conditions, sun gear 110 would normally be urged torotate in a counter clockwise direction resulting in rightward movementwhich compresses spring 113 on shaft 46. The compression springs 166resiliently urge clutch pressure member 122, and clutch backup member124 into frictional engagement with clutch driven member 126. The torqueon shaft 46 is directly imparted to clutch backing 124 via the keyedconnection 123. Similarly, a portion of the torque on clutch backing 124is transmitted to clutch member 122 by reason of the right-hand splinedconnection 180, 182. Because of the helix angle of the splinedconnection 180, 182, the clutch member 122 tends to move toward theright in a direction to become disengaged. However, the force of thesprings 166 overcome this force of disengagement, thereby maintainingclutch member 122 engaged with the other clutch parts 124 and 126. Thusis is seen that, under these conditions, the clutch 122, 124, 126 (120)is engaged. This positive engagement of the clutch 120 positively lockssun gear 110 against rotation with respect to pinion gears 104 andthereby establishes a direct coupling or a unity gear ratio between thefirst shaft 20 and second shaft 30.

To operate the coupling in a reduced ratio mode, i.e., in a conditionwherein the second shaft 30 will be coupled to the first'shaft 20 torotate at a reduced speed with respect thereto, caliper brake 74 ismanually frictionally engaged with brake disk 62. With brake disk 62thus restrained from rotation with respect to housing 12, brake shaft 46is similarly restrained against rotation. As before, ring gear 40 isbeing driven in a clockwise direction and there is a load on secondshaft 30 tending to restrain rotation of pinion carrier 82.Correspondingly, ring gear 40 tends to rotate pinion gears 104 aboutpinion shafts 100 thereby transmitting a counter clockwise torque to sungear 110 which tends to rotate sun gear 110 in a counter clockwisedirection.

Since sun gear is coupled-to brake shaft 46 by spline 114 which isformed in the shape of a left-handed helix, this torque produces anaxial thrust on sun gear 110 which acts to force sun gear 110 to theright (as viewed in FIG. 1). correspondingly, movement of sun gear 110to the right (as viewed in FIG. 1) will permit clutch member 122 to moveto the right by reason of the'unwinding action of the right-hand splinedconnection 180, 182 thereby causing disengagement of the clutch 120.Simultaneously, when clutch member 122 becomes disengaged from clutchmember 126, wave spring 174 will urge clutch driven member 126 to theright (as viewed in FIG. 1) by reason of the axially slidable couplingof clutch driven member 126 to threaded fasteners 98. Thus, it can beseen that when sun gear 110 is forced to the right, clutch isautomatically disengaged. Since sun gear 110 is locked against rotation,ring gear 40 will cause pinion gears 104 to orbit sun gear 110.correspondingly, second shaft 30 will be driven at a reduced ratio byreason of its direct coupling to pinion carrier 82.

Another important feature of the coupling and one which is of particularvalue when the coupling is used as a transmission in a motor vehiclesuch as, for example, a snowmobile, is that it also provides a positivecoupling between the first shaft 20 and second shaft 30 when momentum ofthe vehicle tends to drive the second shaft 30 faster than the firstshaft 20. This positive coupling thus enables braking of the vehicle byreason of engine drag and simultaneously, applies the braking forceapplied by caliper brake 74 on brake disk 62 to second shaft 30. Thusthe caliper brake 74 can also be used as a brake for the vehicle inwhich the transmission 10 is mounted.

In this latter mode of operation, the conjoint action of the variousparts produces firm engagement of the clutch 120 such that the brakedisc 62 in effect is directly coupled to the shaft 30. Thus, applicationof the caliper brake 74 will result in the application of braking torqueto the output shaft 30. This action is as follows:

Due to the momentum of the vehicle, the output shaft 30 becomes thedriver, imparting torque to the remainder of the mechanism. This drivingtorque is applied to the pinion carrier member 84. Because of enginedrag on shaft 20, part of the applied torque will split between theclutch 120 and the carrier flange 86. The portion of the torque appliedto flange 86, thus to pinions 104, is transmitted to sun gear 110 in aclockwise direction (viewing FIG. 1 from the left) causing it to wind onthe helical spline 112, 114 to the left into forceful abutting contactwith the hub of clutch member 122. This abutting contact aids inmaintaining engagement of the clutch 120 by urging clutch member 122toward the left. Spring 113 also aids in maintaining clutch 120 inengagement by urging sun gear 110 toward the left.

The remaining portion of the torque on the carrier 84 splits to theclutch 120 via the hub 88, and clutch member 126, to the two clutchmembers 122 and 124. The torque is here split between these latter twomembers, with the larger portion passing to the member 124, the reasonfor this being the difference in the areas of the friction surfaces onthe two members 122 and 124, respectively. The torque in larger member124 passes directly to the brake shaft 46. The torque on the member 122is in a direction which tends to unwind it via splines 180, 182 fromengagement with members 124, 126.

However, the disengaging force is overcome by the sun gear actionleftward as first explained. Also, the springs 166 aid in maintainingthis clutch engagement.

Thus, application of braking force to the disk 62 by means of caliper 74slows the vehicle.

A further mode of operation involves braking the vehicle againstbackward motion. ln this event, counter clockwise torque appears oncarrier 84. This torque splits between the clutch 120 and the pinionflange 86 as before, but sun gear 110 is now wound on splines 112, 114rightward, compressing spring 113. This separates sun gear 110 from thehub of clutch member 124. Clutch member 124 does not follow thisrightward movement thereby causing disengagement of the clutch 120, butinstead, due to the right-hand helix of spline 180, 182, the member 122winds leftward into engagement with members 126 and 124. This engagementresults in a frictional turning movement being applied to member 122causing it to further wind into tighter engagement thereby producing aself-energizing action of almost infinite capacity.

It will now be seen that the mechanism of this invention, in a uniquemanner, provides for all of the necessary functions in achieving theusual requirements of plural speed drive plus braking action bothforward and reverse.

Referring now to FIG. 3 there is illustrated a two speed gearedtransmission 200 in accordance with the invention which incorporates amodified clutch assembly 202. As in the abovedescribed embodiment,clutch assembly 202 includes a clutch pressure member 204, clutchbacking member 206, and driven member 208. Backing member 206 is carriedon brake shaft 210 and keyed thereto for rotation therewith with asuitable key 212. Clutch driven member 208 is rotatably coupled topinion gear carrier assembly (not shown) as described above in referenceto FIG. 1, and clutch driven member 204 is coupled to clutch backupmember 206 with a right-handed helical spline coupling at 214.

Pressure member 204 is further provided with an annular recess 216 whichhas a rearwardly and outwardly tapered surface 218 and a cylindricalshaft portion 220. Carried on shaft portion 220 is a suitable hub 222which includes an external flange 224 having therethrough a plurality ofholes 226 which are disposed in registry with and engagingly receivepins 156. Hub 222 further includes a radially extending surface 228disposed adjacent recess 216.

Rotatably received in recess 216 in rolling engagement with surface 218thereof and surface 228 of hub 222 are a plurality of steel balls 230.It will now be observed that, with clutch pressure member 204 and hub228 rotating, steel balls 230 will rotate therewith and be urgedradially outwardly by centrifugal force. As the balls 230 try to moveoutwardly, they generate a force on clutch pressure member 204leftwardly (as viewed in FIG. 3) thereby forcing the members of clutch202 into more positive engagement.

It is further observed that a transmission in accordance with theinvention does not provide a neutral coupling. However, this presents nodifficulty since in most, if not all, applications of the transmission,the first shaft will be coupled to a primemover such as an enginethrough a fluid or centrifugal type coupling and the coupling willenable the necessary relative slippage between the prime mover and thetransmission when the prime mover is idling.

It should also be noted that a smooth transition or shift from one gearratio to the other is easily effected by simply applying and releasingthe caliper brake 74 gradually. This action smooths out the engagementand disengagement of the clutch thereby enabling smooth shiftingcharacteristic.

While the above description has been based upon an embodiment of theinvention in which the ring gear is fixedly secured to the first shaftand the sun gear drivingly coupled to the brake shaft, it will beapparent that the coupling could also be constructed with the sun gearfixedly secured to the first shaft and the ring gear drivingly coupled.to the brake shaft with a helical spline.

In a working model of a two speed coupling in accordance with theinvention, the helix angle of the splines 112, 114 is 33 and the helixangle of splines 180, 182 is 15. In this embodiment there are l2 helicalsprings 166 which generate a total engaging pressure on clutch pressuremember 122 of 48 pounds. Wave spring 174 generates a releasing forcebetween clutch backup member 124 and c'iiri'chHfivelYiheinbeEi26 Bf fourpounds. All gears are of the straight spur type, ring gear 40 havingseventy-four teeth, planet gears 104 having twenty teeth, and sun gear110 having thirty-four teeth producing a gear ratio of 1.0 to 1.0 in adirect drive and 1.4594 in reduced coupling mode. FIG. 1 of the drawingsis substantially to scale.

While there have been described above the principles of this inventionin connection with specific apparatus, it is to be clearly understoodthat this description is made only by way of example and not as alimitation to the scope of the invention.

What is claimed is: 1. In a two speed transmission, the combinationcomprising a. an epicyclic gear assembly including a ring gear, a

sun gear and at least one pinion gear, b. a first rotatable shaftdrivingly coupled to one of said ring and sun gears, c. a secondrotatable shaft drivingly coupled to said pinion gear, d. brake meansfor selectively locking and unlocking the other of said ring and sungears against rotation,

e. clutch means coupled between said pinion gear and said other gear forselectively locking said pinion gear to said other gear thereby shiftingbetween low gear to high gear, respectively, said clutch mansincluding 1. a backup member drivingly coupled to said other gear, apressure member drivingly coupled to said backup member, and a drivenmember drivingly coupled to said pinion gear,

2. first helical spline means coupling said backup member to saidpressure member for disengaging same from said driven member in responseto actuation of said brake means and to a first torque between saidpressure member and said driven member in a first rotational direction,thereby providing a shift into low gear,

3. clutch-actuating means responsive to unlocking said braking means forforcibly engaging said pressure, driven and backup members for conjointrotation, thereby providing a shift into high gear, and

4. said clutch-actuating means also being responsive to actuation ofsaid braking means and also torque in a predetermined direction on saidother gear for forcibly engaging said clutch members as aforesaid,thereby providing a braking action.

2. The combination of claim I in which said first helical spline meansis of such angle that upon actuation of said braking means andapplication of a second torque between said pressure and driven membersin a direction opposite to said first rotational direction, said clutchmembers are self-energizingly engaged.

3. The combination of claim 2 wherein said clutchactuating meansincludes first spring means operatively coupled between said pressuremember and said backup member for resiliently urging said pressure andbackup members into frictional engagement with said driven member.

4. The combination of claim 3 wherein said pressure and backup membersinclude flat circular portions disposed coaxially of said first shaft inparallel, spaced apart relationship, one of said circular portionshaving therethrough a plurality of holes in.an annular array, therebeing a plurality of coupling pins each extending through apredetermined one of said holes and having one end thereof fixedlysecured to the other of said cir- .cular portions, the distal ends ofsaid pins being provided with enlarged heads, said holes havingadiameter greater than the diameter of said pins, and said spring meansincluding a plurality of helicalsprings compressibly received on saidpins between said heads and said one circular portion.

5. The combination of claim 3 wherein said driven member is axiallymovable with respect to said backup member, and further including secondspring means for resiliently urging said driven member out of engagementwith said backup member upon occurrence of said first torque.

6. The combination of claim 5 further including a pinion gear carrier,said pinion gear being rotatably journaled thereon, said second springmeans including a wave spring compressibly disposed between said piniongear carrier and said driven member.

7. The combination of claim 2 wherein said pressure member and saidbackup member have concentric, telescopicallyvengaged hub portions, saidfirst spline means including at least one helical male spline on one ofsaid hub portions and disposed at a first predetermined helix angle, anda female spline complementary to said male spline on the other of saidhub portions and operatively engaged therewith.

8. The combination of claim 2 wherein said pressure member and saidother gear are relatively axially movable.

9. The combination of claim 8 wherein sa clutchactuating means furtherincludes third spring mea 18 for resiliently urging said other gear intoabutting engagement with said pressure member in a first axial directionto increase the frictional engagement of said pressure and drivenmembers in response to said predetermined torque.

10. The combination of claim 9 further comprising second helical splinemeans coupling said other gear to said brake means for forcibly urgingsaid other gear in a direction opposite said first axial direction inresponse to locking thereof against rotation and in the absence of saidpredetermined torque.

11. The combination of claim 10 wherein said first spline means includesa first pair of complementary male and female helical splines formed onsaid backup and pressure members and said second spline means includes asecond pair of complementary male and female splines formed on saidbrake means and said other gear, respectively, said first pair ofsplines extending at a first helix angle in a first rotationaldirection, said second pair of splines extending at a second helix anglein a second rotational direction.

12. The combination of claim ll wherein said first helix angle isgreater than said second helix angle and said first rotational directionis opposite to said second rotational direction.

13. The combination of claim l2 wherein said first helix angle is 15,and said second helix angle is 33".

14. The combination of claim 13 wherein said one gear is said ring gearand said other gear is said sun gear.

15. The combination of claim 1 wherein said pressure and backup membershave complementary coaxially disposed frusto-conical surfaces and saiddriven member includes a frusto-conical portion disposed therebetween,said first spline means moving said pressure member and said backupmember axially away from each other to disengage said driven member.

16. The combination of claim 15 wherein said pressure member is axiallymovable with respect to said other gear.

17. The combination of claim 15 including friction increasingliningsfixedly secured to said frusto-conica] portion, said pressure member andsaid backup member engaging said linings when said clutch is engaged.18. The combination of claim 17 wherein said driven member is axiallyrelatively movable with respect to said pinion gear.

19. The combination of claim 1 wherein saidbrake means includes a thirdshaft and a brake disk fixedly se" cured thereto, said first, second,and third shafts being disposed along a common axis and journaled forindependent rotatable movement.

20. The combination of claim 19 wherein said brake further includes amanually operable caliper brake for selectively, frictionally engagingand disengaging said brake disk.

21. The combination of claim 1 further comprising a first housing, saidfirst and second shafts and said brake means being independentlyrotatably journaled therein, and a second housing enclosing saidepicyclic gear assembly, said second housing being rotatable withrespect to said first housing and including seal means for renderingsaid second housing fluid tight.

22. The combination of claim 21 wherein said epicyclic gear assemblyfurther includes a pinion gear carrier, said pinion geare beingrotatably journaled thereon, said carrier forming a part of said secondhousing.

23. The combination of claim 22 wherein said brake means includes athird shaft, said first, second, and third shafts being coaxiallyjournaled within said first housing, said third shaft being rotatablyjournaled on a first portion of said first shaft, said second shaftbeing rotatably journaled on a second portion of said first shaft.

24. The combination of claim 1 wherein said clutch means furtherincludes means responsive to conjoint rotation of said pressure andbackup members for increasing the frictional engagement thereof withsaid driven member.

nular recess having an angled surface thereof extending radiallyoutwardly towards said radially extending surface, and a plurality ofhigh density spherical balls recieved in said annular recess, said ballsbeing simulta' neously engaged with said angled and said radiallyextending surfaces when said pressure member and said hub are rotating.

1. In a two speed transmission, the combination comprising a. anepicyclic gear assembly including a ring gear, a sun gear and at leastone pinion gear, b. a first rotatable shaft drivingly coupled to one ofsaid ring and sun gears, c. a second rotatable shaft drivingly coupledto said pinion gear, d. brake means for selectively locking andunlocking the other of said ring and sun gears against rotation, e.clutch means coupled between said pinion gear and said other gear forselectively locking said pinion gear to said other gear thereby shiftingbetween low gear to high gear, respectively, said clutch meansincluding
 1. a backup member drivingly coupled to said other gear, apressure member drivingly coupled to said backup member, and a drivenmember drivingly coupled to said pinion gear,
 2. first helical splinemeans coupling said backup member to said pressure member fordisengaging same from said dRiven member in response to actuation ofsaid brake means and to a first torque between said pressure member andsaid driven member in a first rotational direction, thereby providing ashift into low gear,
 3. clutch-actuating means responsive to unlockingsaid braking means for forcibly engaging said pressure, driven andbackup members for conjoint rotation, thereby providing a shift intohigh gear, and
 4. said clutch-actuating means also being responsive toactuation of said braking means and also torque in a predetermineddirection on said other gear for forcibly engaging said clutch membersas aforesaid, thereby providing a braking action.
 2. first helicalspline means coupling said backup member to said pressure member fordisengaging same from said dRiven member in response to actuation ofsaid brake means and to a first torque between said pressure member andsaid driven member in a first rotational direction, thereby providing ashift into low gear,
 2. The combination of claim 1 in which said firsthelical spline means is of such angle that upon actuation of saidbraking means and application of a second torque between said pressureand driven members in a direction opposite to said first rotationaldirection, said clutch members are self-energizingly engaged.
 3. Thecombination of claim 2 wherein said clutch-actuating means includesfirst spring means operatively coupled between said pressure member andsaid backup member for resiliently urging said pressure and backupmembers into frictional engagement with said driven member. 3.clutch-actuating means responsive to unlocking said braking means forforcibly engaging said pressure, driven and backup members for conjointrotation, thereby providing a shift into high gear, and
 4. saidclutch-actuating means also being responsive to actuation of saidbraking means and also torque in a predetermined direction on said othergear for forcibly engaging said clutch members as aforesaid, therebyproviding a braking action.
 4. The combination of claim 3 wherein saidpressure and backup members include flat circular portions disposedcoaxially of said first shaft in parallel, spaced apart relationship,one of said circular portions having therethrough a plurality of holesin an annular array, there being a plurality of coupling pins eachextending through a predetermined one of said holes and having one endthereof fixedly secured to the other of said circular portions, thedistal ends of said pins being provided with enlarged heads, said holeshaving a diameter greater than the diameter of said pins, and saidspring means including a plurality of helical springs compressiblyreceived on said pins between said heads and said one circular portion.5. The combination of claim 3 wherein said driven member is axiallymovable with respect to said backup member, and further including secondspring means for resiliently urging said driven member out of engagementwith said backup member upon occurrence of said first torque.
 6. Thecombination of claim 5 further including a pinion gear carrier, saidpinion gear being rotatably journaled thereon, said second spring meansincluding a wave spring compressibly disposed between said pinion gearcarrier and said driven member.
 7. The combination of claim 2 whereinsaid pressure member and said backup member have concentric,telescopically engaged hub portions, said first spline means includingat least one helical male spline on one of said hub portions anddisposed at a first predetermined helix angle, and a female splinecomplementary to said male spline on the other of said hub portions andoperatively engaged therewith.
 8. The combination of claim 2 whereinsaid pressure member and said other gear are relatively axially movable.9. The combination of claim 8 wherein said clutch-actuating meansfurther includes third spring means for resiliently urging said othergear into abutting engagement with said pressure member in a first axialdirection to increase the frictional engagement of said pressure anddriven members in response to said predetermined torque.
 10. Thecombination of claim 9 further comprising second helical spline meanscoupling said other gear to said brake means for forcibly urging saidother gear in a direction opposite said first axial direction inresponse to locking thereof against rotation and in the absence of saidpredetermined torque.
 11. The combination of claim 10 wherein said firstspline means includes a first pair of complementary male and femalehelical splines formed on said backup and pressure members and saidsecond spline means includes a second pair of complementary male andfemale splines formed on said brake means and said other gear,respectively, said firSt pair of splines extending at a first helixangle in a first rotational direction, said second pair of splinesextending at a second helix angle in a second rotational direction. 12.The combination of claim 11 wherein said first helix angle is greaterthan said second helix angle and said first rotational direction isopposite to said second rotational direction.
 13. The combination ofclaim 12 wherein said first helix angle is 15*, and said second helixangle is 33*.
 14. The combination of claim 13 wherein said one gear issaid ring gear and said other gear is said sun gear.
 15. The combinationof claim 1 wherein said pressure and backup members have complementarycoaxially disposed frusto-conical surfaces and said driven memberincludes a frusto-conical portion disposed therebetween, said firstspline means moving said pressure member and said backup member axiallyaway from each other to disengage said driven member.
 16. Thecombination of claim 15 wherein said pressure member is axially movablewith respect to said other gear.
 17. The combination of claim 15including friction increasing linings fixedly secured to saidfrusto-conical portion, said pressure member and said backup memberengaging said linings when said clutch is engaged.
 18. The combinationof claim 17 wherein said driven member is axially relatively movablewith respect to said pinion gear.
 19. The combination of claim 1 whereinsaid brake means includes a third shaft and a brake disk fixedly securedthereto, said first, second, and third shafts being disposed along acommon axis and journaled for independent rotatable movement.
 20. Thecombination of claim 19 wherein said brake further includes a manuallyoperable caliper brake for selectively, frictionally engaging anddisengaging said brake disk.
 21. The combination of claim 1 furthercomprising a first housing, said first and second shafts and said brakemeans being independently rotatably journaled therein, and a secondhousing enclosing said epicyclic gear assembly, said second housingbeing rotatable with respect to said first housing and including sealmeans for rendering said second housing fluid tight.
 22. The combinationof claim 21 wherein said epicyclic gear assembly further includes apinion gear carrier, said pinion gear being rotatably journaled thereon,said carrier forming a part of said second housing.
 23. The combinationof claim 22 wherein said brake means includes a third shaft, said first,second, and third shafts being coaxially journaled within said firsthousing, said third shaft being rotatably journaled on a first portionof said first shaft, said second shaft being rotatably journaled on asecond portion of said first shaft.
 24. The combination of claim 1wherein said clutch means further includes means responsive to conjointrotation of said pressure and backup members for increasing thefrictional engagement thereof with said driven member.
 25. Thecombination of claim 24 wherein said engagement increasing meansincludes an annular recess in said pressure member, a hub drivinglycoupled to said backup member and having a radially extending surfacethereon disposed adjacent said recess, said annular recess having anangled surface thereof extending radially outwardly towards saidradially extending surface, and a plurality of high density sphericalballs received in said annular recess, said balls being simultaneouslyengaged with said angled and said radially extending surfaces when saidpressure member and said hub are rotating.